多线程

多线程实验

1.创建线程  定义线程函数  保护线程，退出时清除资源   定义清除函数

2.当主进程中用pthread_join时，先执行线程，主进程等待相应线程执行结束，再执行。

  否则，先执行主进程，主进程中若sleep，则执行线程，否则主进程直接执行结束。

 

 

#include <pthread.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
int a = 1;

void *clean(void *arg)
{
    printf("cleanup :%s\n", (char *)arg);    //change the type of arg

    return (void *)0;    //the type of return is *p

}
void *pth1 (void *arg)
{
    pthread_cleanup_push((void *)clean, "thread 1"); //resource recovery

    int *num;
    num = (int *)arg;    //change the type of parametre

    a++;
    printf("pthread:a = %d\n", a);
    printf("the num=%d\n", *num);
    pthread_exit((void *)1);
    pthread_cleanup_pop(0); //resource recovery when exit

    return (void *)0;
}

main(void)
{
    int num = 4;
    pthread_t tidp;
    a++;
    int *arg = &num;    //change the type of parametre

    if(pthread_create(&tidp, NULL,(void *)pth1,(void *)arg) < 0)
    {
        printf("create error:%s\n", strerror(errno));
        exit(1);
    }
    pthread_join(tidp,NULL);
    printf("main:a = %d\n", a);
//    sleep(1);

    printf("this is process!\n");
}


易错点：

1.pthread_create 函数中参数的类型

2.void *pth1 (void *arg) 线程函数为返回值为指针的函数